Honestly I wouldn't call them bros, as that's just copying PewDiePie. Try to be unique, it will make you stand out a lot more.
When it comes to naming your subscribers, it should come naturally to you. A lot of times the viewers come up with their own names. I would just keep creating content, and wait until you find yourself calling them something naturally without really knowing it.
You also don't really need to call them anything. It's not something you have to do, so if you can't come up with anything, don't worry about it.